Cyanine dyes



United States Patent 3,515,722 CYANINE DYES Earl J. Van Lare, Rochester,N.Y., assignor to Eastman Kodak Company, Rochester, N.Y., a corporationof New Jersey No Drawing. Filed Dec. 23, 1966, Ser. No. 604,161 Int. Cl.C09b 23/00 U.S. Cl. 260-240 11 Claims ABSTRACT OF THE DISCLOSURE Cyaninedyes are provided which have the following general formula:

wherein m represents a positive integer of from 1 to 2; n represents apositive integer of from 2 to 3; L represents a methine linkage; Rrepresents a member selected from the group consisting of an alkyl groupof from 1 to 4 carbon atoms, an alkenyl group, and a phenyl group; R andR each represents a member selected from the group consisting of ahydrogen atom, an alkyl group of from 1 to 4 carbon atoms and a phenylgroup; R represents a member selected from the group consisting of analkyl group of from 1 to 4 carbon atoms and a phenyl group; X representsan acid anion; and, Z represents the nonmetallic atoms necessary tocomplete a desensitizing heterocyclic nucleus containing 5 to 6 atoms inthe heterocyclic ring, said desensitizing nucleus being selected fromthe group consisting of nitrobenzothiazole, nitrobenzoselenazole,imidazo[4,5-b]quinoxaline, 3,3-dialkyl-3H-pyrrolo[2,3-b1pyridine,3,3-dialkyl-3H-dialkyl- 3H-nitroindole, thiazolo[4,5-b1quinoline,nitroquinoline, nitrothiazole, nitronaphthothiazole, nitrooxazole,nitronap'hthoxazole, nitroselenazole, nitronaphthoselenazole andnitropyridine nuclei. The dyes of this invention are electron acceptorsand spectral sensitizers for fogged direct positive silver halideemulsions.

This invention relates to novel photographic materials, and moreparticularly to a new class of cyanine dyes containing a 4-pyrazolylnucleus that are especially useful as electron acceptors and spectralsensitizers for direct positive photographic silver halide emulsions,and to means for the preparation of such new dyes.

It is known that direct positive images can be obtained with certaintypes of photographic silver halide emulsions. For example, photographicemulsions have been proposed for this purpose comprising an electronacceptor and silver halide grains that have been fogged with acombination of a reducing agent and a compound of a metal moreelectropositive than silver. One of the advantages of such directpositive emulsions is that the highlight areas of the images obtainedwith these materials are substantially free from fog. However, knownmaterials of this type have not exhibited the high speed required formany applications of photography. Also, such known materials have notshown the desired selective sensitivity, especially to radiation in thegreen to red region of the spectrum. It is evident, therefore, thatthere is need in the art for improved direct positive photographicmaterials having both good speed and desirable sensitivity to longerwavelength radiations.

I have now found that certain cyanine dyes containing certain pyrazolenuclei are outstanding electron acceptors and spectral sensitizers indirect positive type photographic silver halide emulsions. They providesuperior reversal systems, especially with fogged silver halideemulsions that are characterized by both good speed and desiredsensitivity to radiation in the green to red region of the spectrum withmaximum sensitivity occurring in most cases in the region of about460550 me. The images produced with these new direct positivephotographic emulsions are clear and sharp.

It is, accordingly, an object of this invention to provide a new classof cyanine dyes that function as electron acceptors and spectralsensitizers for photographic silver halide emulsions, and moreparticularly for direct positive photographic emulsions, such as fogged,direct positive emulsions. Another object is to provide means forpreparing the new cyanine dyes of this invention. Other objects of thisinvention will be apparent from this disclosure and the appended claims.

The new class of cyanine dyes of the invention include those comprisingfirst and second 5- to G-membered nitrogen heterocyclic nuclei joined bymethine linkage; the first of said nuclei being a pyrazole nucleusjoined, by the 4-carbon atom thereof, to the methine linkage, saidsecond nucleus being a desensitizing quaternary salt nucleus joined by acarbon atom thereof to the methine. linkage; and, said methine linkagebeing selected from the group consisting of a dimethine linkage and atetramethine linkage.

One highly useful class of the novel cyanine dye compounds of theinvention include those represented by the following general formula:

wherein m represents a positive integer of from 1 to 2; n represents apositive integer of from 2 to 3; L represents a methine linkage, e.g.,CH=, C(CH C(C H etc.; R represents an alkyl group, including substitutedalkyl (preferably a lower alkyl containing from 1 to 4 carbon atoms),e.g., methyl, ethyl, propyl, isopropyl, butyl, hexyl, cyclohexyl, decyl,dodecyl, etc., or a substituted alkyl group (preferably a substitutedlower alkyl containing from 1 to 4 carbon atoms), such as a hydroxyalkylgroup, e.g., fl-hydroxyethyl, w-hYdIOXY- butyl, etc., an alkoxyalkylgroup, e.g., ,B-methoxyethyl, w-butoxybutyl, etc., a carboxyalkyl group,e.g., fi-carboxyethyl, w-carboxybutyl, etc., a sulfoalkyl group, e.g.,[3- sulfoethyl, w-sulfobutyl, etc., a sulfatoalkyl group, e.g., B-sulfatoethyl, w-sulfatobutyl, etc., an acryloxyalkyl group, e.g.,B-acetoxyethyl, y-acetoxypropyl, w-butyryloxybutyl, etc., analkoxycarbonylalkyl group, e.g., p-methoxycarbonylethyl,w-ethoxycarbonylbutyl, etc., or an aralkyl group, e.g., benzyl,phenethyl, etc., and the like, or an alkenyl group, e.g., allyl,l-propenyl, Z-butenyl, etc., or an aryl group, e.g., phenyl, tolyl,naphthyl, methoxyphenyl, chlorophenyl, etc.; R and R each represents ahydrogen atom, or an alkyl group (preferably a lower alkyl containingfrom 1 to 4 carbon atoms), e.g., methyl, ethyl, propyl, isopropyl,butyl, hexyl, cyclohexyl, decyl, dodecyl, etc., or an aryl group e.g.,phenyl, tolyl, xylyl, methoxyphenyl, chlorophenyl, naphthyl, etc.; Rrepresents an alkyl group, preferably a lower alkyl containing from 1 to4 carbon atoms, e.g., methyl, ethyl, propyl, isopropyl, butyl, hexyl,cyclohexyl, decyl, dodecyl, etc., or an aryl group e.g., phenyl, tolyl,xylyl, methoxyphenyl, chlorophenyl, naphthyl, trifluorophenyl,pentafluorophenyl, etc.; X represents an acid anion, e.g., chloride,

bromide, iodide, p-toluenesulfonate, thiocyanate, sulfamate, methylsulfate, ethyl sulfate, perchlorate, etc.; and Z represents thenonmetallic atoms necessary to complete a densensitizing heterocyclicnucleus selected from the group including a nitrobenzothiazole nucleus,e.g., S-nitrobenzothiazole, 6-nitrobenzothiazole, chloro-6-nitro-:benzothiazole, etc.; a nitrobenzoxazole nucleus, e.g.,S-nitrobenzoxazole, 6-nitrobenzoxazole, 5-chloro-6-nitrobenzoxazole,etc.; nitrobenzoselenazole nucleus, e.g., S-nitrobenzoselenazole,fi-nitrobenzoselenazole, 5-chlo1o- 6-nitrobenzoselenazole, etc.; animidazo[4,5-b]quinoxaline nucleus, e.g., imidazo[4,5-'b]quinoxaline,1,3-dialkylimidazo[4,5-b]quinoxaline such as 1,3-diethylimidazo-[4,5-b]quinoxaline, 6 chloro-l,3-diethylamidazo[4,5-b] quinoxaline,etc., 1,3-dialkenylimidazo[4,5-b1quinoxaline such as1,3-diallylimidazo[4,5-b]quinoxaline, 6-chloro- 1,3 diallylimidazo[4,5b1quinoxaline, etc., 1,3-diarylimidazo[4,5-b]quinoxaline such as1,3-diphenylimidazo- [4,5-b1quinoxaline,6-chloro-1,3-diphenylimidazo[4,542] quinoxaline, etc.; a3,3-dialkyl-3H-pyrrolo[2,3-b]pyridine nucleus, e.g.,3,3-dimethyl-3H-pyrrolo[2,3-b1pyridine,3,3-diethyl-3H-pyrrolo[2,3-b1pyridine, etc.; a 3,3-dialkyl-3H-nitroindole, e.g., 3,3-dimethyl-5-nitro-3H-indole,3,3-diethyl-5-nitro-3H-indole, 3,3-dimethyl-6-nitro- 3H-indole, etc., athiazolo[4,5-b]quinoline nucleus; or a nitroquinoline, e.g.,S-nitroquinoline, 6-nitroquinoline, etc. Other nuclei containing nitrogroups that are useful as desensitizers include nitrothiazole,nitronaphthothiazole, nitrooxazole, nitronaphthoxazole, nitroselenazole,nitronaphthoselenazole, and nitropyridine nuclei. The desensitizingnuclei wherein Z in above Formula I represents the atoms necessary tocomplete a nitro substituted heterocyclic nucleus form particularlyeflicacious desensitizing dyes and are a preferred dye species of theinvention.

The cyanine dyes of the invention are powerful desensitizers forpreparing direct positive photographic silver halide emulsions. Inaddition, they are also useful desensitizers in emulsions used in theprocess described in Stewart and Reeves, US. Pat. No. 3,250,618, issuedMay 10, 1966.

As used herein and in the appended claims, desensitizing nucleus refersto those nuclei which, when converted to a symmetrical carbocyanine dyeand added to gelatin silver chlorobromide emulsion containing molepercent chloride and mole percent bromide, at a concentration of from0.01 to 0.2 gram dye per mole of silver, cause by electron trapping atleast about an percent loss in the blue speed of the emulsion whensensitometrically exposed and developed three minutes in Kodak developerD-l9 at room temperature. Advantageously, the desensitizing nuclei arethose which, when converted to a symmetrical carbocyanine dye and testedas just described, essentially completely desensitize the test emulsionto blue radiation (i.e., cause more than about to loss of speed to blueradiation).

The cyanine dyes defined by Formula I above are conveniently prepared byheating a mixture of (1) a heterocyclic compound of the formula:

wherein m, R X and Z are as previously defined, and

(2) a pyrazole compound of the formula:

III. R2

R4N i1\ o -L=L 1oto wherein n, L, R R and R are as previously defined,in approximately equimolar proportions, in the presence of a condensingagent, if desired, such as anhydrous sodium acetate, a trialkylaminesuch as triethylamine, etc., piperidine, N-methylpiperidine, etc.,-in aninert solvent medium such as ethanol, acetic anhydride, glacial aceticacid, etc. The crude dyes are then separated from the reaction mixturesand purified by one or more recrystallizations from appropriate solventssuch as benzene, petroleum ether, ethanol, methanol, etc.

In the preparation of direct positive photographic silver halideemulsions, one or more of the new dyes of the invention, as defined byFormula I above, are incorporated into direct positive type emulsions,especially into a suitably fogged silver halide emulsion. The emulsioncan be fogged in any suitable manner, such as by light or with chemicalfogging agents, e.g., stannous chloride, formaldehyde, thiourea dioxideand the like. The emulsion may be fogged by the addition thereto of areducing agent such as thiourea dioxide and a compound of a metal moreelectropositive than silver such as a gold salt, for example, potassiumchloroaurate, as described in British Pat. 723,019 (1955).

Typical reducing agents that are useful in providing such emulsionsinclude stannous salts, e.g., stannous chloride, hydrazine, sulfurcompounds such as thiourea dioxide, phosphonium salts such as tetra(hydroxymethyl) phosphonium chloride, and the like. Typical useful metalcompounds that are more electropositive than silver include gold,rhodium, platinum, palladium, iridium, etc., preferably in the form ofsoluble salts thereof, e.g., potas-. sium chloroaurate, auric chloride,(NH PdCl and the like.

The concentration of added dye can vary widely, e.g., from about 50 to2000 mg. and preferably from about 400 to 800 mg. per mole of silverhalide in the direct positive emulsions.

As used herein, and in the appended claims, fogged refers to emulsionscontaining silver halide grains which produce a density of at least 0.5when developed, without exposure, for 5 minutes at 68F. in developerKodak DK-SO having the composition set forth below, when the emulsion iscoated at a silver coverage of 50 mg. to 500 mg. per square foot.

DEVELOPER N-methyl-p-aminophenol sulfate2.5 g. Sodium sulfite(anhydrous)30.0 g. Hydroquinone2.5 g.

Sodium metaborate10.0 g.

Potassium bromide-05 g.

Water to make-1.0 l.

The dyes of this invention are also advantageously incorporated indirect positive emulsions of the type-in which a silver halide grain hasa water-insoluble silver salt center and an outer shell composed of afogged waterinsoluble silver salt that develops to silver withoutexposure. The dyes of the invention are incorporated,

preferably, in the outer shell of such emulsions. These emulsions can beprepared in various ways, such as those described in Berriman US. Pat.application Ser. No. 448,467, filed Apr. 15, 1965. For example, theshell of the grains in such emulsions may be prepared by precipitatingover the core grains a light-sensitive waterinsoluble silver salt thatcan be fogged and which fog is removable by bleaching. The shell is ofsufiicient thickness to prevent access of the developer used inprocessing the emulsions of the invention to the core. The silver saltshell is surface fogged to make developable tometallic silver withconventional surface image developing compositions. The silver salt ofthe shell is sufficiently fogged to produce a density of at least about0.5 when developed for 6 minutes at 68 F. in Developer A below when theemulsion is coated at a silver coverage of mg. per square foot. Suchfogging can be effected by chemically sensitizing to fog with thesensitizing agents described for chemically sensitizing the coreemulsion, high intensity light and the like fogging means well known tothose skilled in the art. While the core need not be sensitized to fog,the shell is fogged. Fogging by means of a reduction sensitizer, a noblemetal salt such as gold salt plus a reduction sensitizer, a sulfursensitizer, high pH and low pAg silver halide precipitating conditions,and the like can be suitably utilized. The shell portion of the subjectgrains can also be coated prior to fogging.

DEVELOPER A N-methyl-p-aminophenol sulfate-25 grams Ascorbic acid-10.0grams Potassium metaborate35.0 grams Potassium bromide-1.0 grams Waterto1 liter Before the shell of water-insoluble silver salt is added tothe silver salt core, the core emulsion is first chemically orphysically treated by methods previously described in the prior art toproduce centers which promote the deposition of photolytic silver, i.e.,latent image nucleating centers. Such centers can be obtained by varioustechniques as described herein. Chemical sensitization techniques of thetype described by Antoine Hautot and Henri Saubeneir in Science etindustries Photographiques, vol. XXVIII, January 1957, pages 1 to 23 andJanuary 1957, pages 57 to 65 are particularly useful. Such chemicalsensitization includes three major classes, namely, gold or noble metalsensitization, sulfur sensitization, such as by a labile sulfurcompound, and reduction sensitization, e.g., treatment of the silverhalide with a strong reducing agent which introduces small specks ofmetallic silver into the silver salt crystal or grain.

In the preparation of the above photographic emulsions, the dyes,reducing agents and metal compounds of the invention are advantageouslyincorporated in the washed, finished silver halide emulsion and should,of course, be uniformly distributed throughout the emulsion. The methodsof incorporating dyes and other addenda in emulsions are relativelysimple and well known to those skilled in the art of emulsion making.For example, it is convenient to add them from solutions in appropriatesolvents, in which case the solvent selected should be completely freefrom any deleterious effect on the ultimate light-sensitive materials.Methanol, isopropanol, pyridine, water, etc., alone or in admixtures,have proven satisfactory as solvents for this purpose. The type ofsilver halide emulsions that can be sensitized with the new dyes includeany of those prepared with hydrophilic colloids that are known to besatisfactory for dispersing silver halides, for example, emulsionscomprising natural materials such as gelatin, albumin, agar-agar, gumarabic, alginic acid, etc. and hydrophilic synthetic resins such aspolyvinyl alcohol, polyvinyl pyrrolidone, cellulose esthers, partiallyhydrolyzed cellulose acetate, and the like.

The dyes, reducing agents and metal compounds of the invention can beused with emulsions prepared with any of the light-sensitive silverhalide salts including silver chloride, silver bromide, silverchlorobromide, silver bromoiodide, silver chlorobromoiodide, etc.Particularly useful are direct positive fogged emulsions in which thesilver salt is a silver bromohalide comprising more than 50 mole percentbromide. As indicated previously, certain dyes of this invention arealso useful in emulsions which contain color formers. This is unexpectedsince related prior art dyes cannot be used in emulsions containing acolor former.

The novel emulsions of this invention may be coated on any suitablephotographic support, such as glass, film base such as celluloseacetate, cellulose acetate butyrate, polyesters such as polyethyleneterephthalate, paper, baryta coated paper, polyolefin coated paper,.e.g., polyethylene or polypropylene coated paper, which may be electronbombarded to promote emulsion adhesion, to produce the novelphotographic elements of the invention.

The invention is further illustrated by the following examples.

EXAMPLE 1 l,3-diallyl-2-[ (3 ,5 -dimethyl- 1-phenyl-4-pyrazolyl) -vinyl]imidazo[4,5-b]quinoxaliniurn iodide A mixture of 2.2 g. (1 mol.) of1,3-diallyl-2-methylimidazo[4,5-b]quinoxalinium p-toluenesulfonate, 1.1g. (1 -mo1.+10% excess) of 3,5-dimethyl-1-phenyl-4-pyrazolecarboxaldehyde, and 15 ml. of acetic anhydride was refluxed for 10minutes. The reaction mixture was chilled and treated with 1 00 ml. ofether. The oily layer was separated from the supernatant liquid bydecantation and then washed with ether. The oily layer was dissolved inacetone and treated with an aqueous solution of sodium iodide. Afterchilling, the crude dye was collected on a filter and washed with waterand then acetone. After recrystallization from methyl alcohol, 1.1 g.(38%) of pure dye was obtained as yellow crystals, M.P. 202203 C.,decomposes.

Analysis.Calcd for C H IN (percent): I, 22.10. Found (percent): I, 22.0.

The above prepared dye containing the desensitizing1,3-diallylimidazo[4,5-b]quinoxalinium salt nucleus was photographicallytested for its usefulness as an electron acceptor and spectralsensitizer for fogged direct positive photographic silver halideemulsions by the following procedure.

A gelatin silver bromoiodide emulsion is reduction and gold sensitized,i.e., fogged, by first adding stannous chloride and heating for minutesat 55 C. and then adding potassium chloroaurate and heating for 20minutes at 55 C., as described in British Pat. 723,019. The aboveprepared dye1,3-diallyl-2-[3,S-dimethyl-l-phenyl-4-pyrazolyl)viny1]imidazo[4,5-b]quinoxaliniumiodide is then added to the above fogged emulsion in amount sufficientto give a concentration of 0.50 gram of the dye per mole of silver. Theresulting emulsion is then coated on a cellulose acetate film support ata coverage of mg. of silver and 400 mg. of gelatin per square foot ofsupport.

A sample of the coated support is then exposed on an Eastman Ibsensitometer using a tungsten light source and processed for 6 minutesat room temperature in Kodak D-19 developer which has the followingcomposition:

N-methyl-p-aminophenol sulfate2.0 g. Sodium sulfite (anhydrous)9 0.0 g.Hydroquinone8.0 g.

Sodium carbonate (monohydrate)52.5 g. Potassium bromide-5.0 g.

Water to make 1.0 liter then fixed, washed and dried. The results arelisted in Table I hereinafter. Referring thereto, it will be seen thatthe dye of this example has a maximum density in the unexposed areas of1.76 and a minimum density in exposed areas of 0.03, a maximumsensitivity of 485 my. and a relative speed of 603. This resultindicates that the dye compound of the above example is especially wellsuited to function as both an electron acceptor and spectral sensitizer.It thus provides excellent quality direct positive photographic silverhalide emulsions. Excellent magenta images are obtained when the colorformer 1-(2,4,6-trichlorophenyl) 3,3 (2",4" di tamylphenoxyacetamido)benzimidazo-S-pyrazolone is incorporated in theemulsion of this example, the emulsion is coated on a support, exposedto a tungsten source through Wratten filter No. 61 and No. 16, andreversal processed as described in Graham et al. U.S. Pat. 3,046,129,issued July 24, 1962, in Example (a) col. 27, lines 27 et seq. exceptthat black-and-white (MQ) development is omitted, the color developmentis reduced to one minute and is conducted in total darkness until afterfixing.

The following Example A containing a sensitizing 3- ethylbenzothiazoliumiodide nucleus in place of the desensitizing1,3-diallylimidazo[4,5-b]quinoxalinium iodide nucleus of above Example1, but otherwise of similar structure, is included here for comparisonpurposes.

EXAMPLE A 2- (3 ,5 -dimethyll-phenyl-4-pyrazolyl) vinyl]-3-ethylbenzothiazolium iodide A mixture of 1.5 g. (1 mol.) of3-ethyl-2-methylbenzothiazolium iodide, 1 g. (1 mol.) of3,5-dimethyl-1-phenyl- 4-pyrazole carboxaldehyde, 1.2 g. (1 mol.+200%excess) of anhydrous sodium acetate, and 10 ml. of ethyl alcohol wasrefluxed one hour. After adding 100 ml. of water and chilling, a reddishtar Was separated from the supernatant liquor by decantation. The tarwas treated with 100 ml. of chloroform and chilled. The crude dye wascollected on a filter and washed with chloroform. The dye was purifiedby recrystallization from methyl alcohol. A yield of 0.9 g. (38%) ofpure dye was obtained as bright yellow crystals, M.P. 225-226 C., dec.

Analysis.--Cald for C H IN S (percent): I, 26.05. Found (percent): I,26.3.

The above dye was photographically tested by the exact proceduredescribed in above Example 1. The results are shown in Table 1hereinafter. Referring to the table, it will be seen that the dye ofExample A containing the sensitizing nucleus had a relative speed ofonly 191 as compared with 603 for the dye of Example 1 containing thespecified desensitizing nucleus. It will be further noted that the dyeof Example A had a maximum density in the unexposed areas of only 1.50and a relatively high minimum density in the exposed areas of 0.14,whereas the dye of Example 1 showed densities of 1.76 and 0.03,respectively, thereby indicating a marked superiority in contrast overthat of Example A. The maximum sensitization for Example A was 455 mwhile that of Example 1 was at 485 m Accordingly, these results indicatethat the dye of Example 1 containing a desensitizing nucleus is markedlysuperior to dyes containing a sensi tizing nucleus, as exemplified byExample A, as an elec' tron acceptor and spectral sensitizer for foggeddirect positive photographic silver halide emulsions.

EXAMPLE 2 2 (3,5 -dimethyl- 1 -phenyl-4-pyrazolyl vinyl] 1 ,3-diethyl-imidazo [4,5 -b] quinox alinium iodide /N 01/ LE.

8 with ether. The oily layer was dissolved in acetone and treated withan aqueous solution of sodium iodide. After chilling, the crude dye wascollected on a filter and washed with water and then with acetone. Afterrecrystallization from ethyl alcohol, 0.45 g. (16%) of pure dye wasobtained as yellow needles, M.P. 237238 C., dec.

EXAMPLE 3 6-chloro-2-[(3,5-dimethyl 1 phenyl-4-pyrazolyl)vinyl]-1,3-diphenylimidazo [4,5-b] quinoxalinium p-toluenesulfonate A mixtureof 2.7 g. (1 mol.) of 6-chloro-2-methyl-1,3-diphenylimidazo[4,5-b].quinoxalinium p-toluenesulfonate, 1.1 g. (1mol.-+l0% excess) of 3,5-dimethyl-1-phenyl- 4-pyrazole carboxaldehyde,and 10 ml. of acetic anhydride was refluxed for ten minutes. Thereaction mixture was chilled and then treated with 100 ml. of ether. The

oily layer was separated from the supernatant liquid by decantation, andthen washed with ether, whereupon it became crystalline. The crude dyewas collected on a lilter and washed with ether. After recrystallizationfrom ethyl alcohol, 1.6 g. (42%) of pure dye was obtained as smallbright yellow crystals, M.P. 283-2 84 C., dec..

Analysis.Calcd for C H ClN O S (percent): C, 67.88; H, 4.59. Found(percent): C, 68.0; H, 4.7.

EXAMPLE 4 2- 3,5 -dimethyll-phenyl-4-pyrazolyl) vinyl] 1 ,3-

diphenylimidazo [4,5-b] quinoxalinium iodide A mixture of 2.6 g. (1mol.) of 2-methyl-1,3-diphenylimidazo[4,5-b]quinoxaliniump-toluenesulfonate, 1.1 g. (l mol.+10% excess) of3,5-dimethyl-l-phenyl-4-pyrazolecarboxaldehyde and 15 ml. of aceticanhydride was refluxed ten minutes. The reaction mixture was chilled andtreated with 100 ml. of ether. The oily layer was separated from thesupernatant liquid by decantation and then washed with ether. The oilylayer was dissolved in acetone and treated with an aqueous solution ofsodium iodide. After chilling, the crude dye was collected on a filterand washed with water and then acetone. After recrystallization frommethyl alcohol, 1.5 g. (47%) of pure dye was obtained as yellowcrystals, M.P. 3l9320 C., dec.

EXAMPLE 5 1,3 diallyl-6-chloro-2-(3,5-dimethyl-1-pheny1-4-pyrazolyl)vinyl] imidazo [4,5-b] quinoxaliniump-toluene- A mixture of 2.35 g. (1 mol.) of 1,3-diallyl-6-chloro-Z-methylimidazo [4,5-b] quinoxalinium p-toluenesulfonate, 1 g. (1 mol.)of 3,5-dimethyl-1-phenyl-4-pyrazole carboxaldehyde, and 10 ml. of aceticanhydride was refluxed EXAMPLE 6 1,3 -diallyl-6-chloro-2-[ 1,3 ,5-trimethyl-4-pyrazolyl) vinyl] imidazo [4,5-b] quinoxaliniump-toluenesulfonate o H2=0 lit-(J H2 A mixture of 2.3 g. (1 mol.) of1,3-diallyl-6-chloro-2- methylimidaz[4,5 b] quinoxaliniump-toluenesulfonate, 0.75 g. (1 mol.) of 1,3,5-trimethyl-4-pyrazolecarboxaldehyde, and ml. of acetic anhydride was refluxed ten minutes.The reaction mixture was chilled and treated with 100 m1. of ether. Thecrude dye was collected on a filter and washed with ether. Afterrecrystallization from ethyl alcohol, 1.7 g. (57%) of pure dye wasobtained as yellow-orange crystals, M.P. l22l24 C., dec.

The intermediate 1,3,5-trimethyl-4-pyrazole carboxaldehyde employed inabove Example 6 was prepared as follows:

A solution of 42 g. (1 mol.+l0% excess) of phosphoryl chloride in 100ml. of dioxane was added to a solution of g. (l mol.+10% excess) ofdimethylforrnamide in 100 ml. of dioxane. Then, a solution of 27.5 g. (1mol.) of 1,3,5-trimethylpyrazone in 50 ml. of dioxane was added dropwisewith stirring. After the addition was complete, the reaction mixture washeated two hours on a steam bath. After cooling, a solution of 120 ml.of about 8% sodium hydroxide was added. The reaction mixture was cooledand the solid collected on a filter and then discarded. Solid sodiumcarbonate was added until effervescence ceased. The reaction mixtureseparated into three layers and the bottom aqueous layer was discarded.The upper two layers were continuously extracted with ether for twohours. The ether extract was concentrated and the residue distilledunder reduced pressure. When the temperature of the vapors reachedl15/15 mm. distillation was stopped and the residue considered goodmaterial. A yield of 17.3 g. (50%) of brownish solid was obtained. Asample recrystallized from ethyl alcohol had M.P. 82-83 C.

The 1,3,5-trimethylpyrazole intermediate was prepared as follows:

To a solution of 23 g. (1 mol.) of methyl hydrazine in 100 ml. of ethylalcohol was added 50 g. (1 mol.) of 2,4-pentanedione over a period ofminutes with stirring, keeping the temperature below by means of an icebath. After the addition was complete, the reaction mixture was refluxedone hour. The reaction mixture was then fractionated through a column. Ayield of 44 g. (80%) of colorless liquid with a B.P. of 167-168" C. wasobtained.

The above prepared dyes of Examples 2 to 6 containing in each case adesensitizing imidazo[4,5-b]quinoxalinium salt nucleus were tested bythe exact procedure described in above Example 1 and found, as shown inTable 1, to have relative speeds of 295, 575, 398, 380 and 436,respectively. These results indicate, together with the other data C-CHOof Table 1, that the above dyes are markedly superior to the comparisondye of Example A which had a speed of only 191. Accordingly, the dyes ofthe above examples qualify as good electron acceptors and spectralsensitizers for fogged, direct positive photographic emulsions.

EXAMPLE 7 2- (3,5-dimethyl-l-phenyl-4-pyrazolyl) vinyl] -3-ethyl-6-nitro-benzothiazolium p-toluenesulfonate A mixture of 4 g. (1 mol.) of3-ethyl-2-methyl-6-nitrobenzothiazolium p-toluenesulfonate, 2 g. (1mol.) of 3,5- dimethyl-l-phenyl-4-pyrazole carboxaldehyde, and 20 ml. ofacetic anhydride was refluxed for ten minutes. The reaction mixture waschilled and then treated with ml. of ether. The oily layer was separatedfrom the supernatant liquid by decantation and washed with ether andthen treated with acetone and chilled. The crude dye was collected on afilter and Washed with acetone. After recrystallization from ethylalcohol, 4.5 g. (79%) of pure dye was obtained as brownish yellowneedles, M.P. 202- 204 C., dec.

Analysis.--Calcd for C H N O S (percent): 60.39; H, 4.89. Found(percent): C, 60.1; H, 4.7.

This dye contains the desensitizing 6-nitrobenzothiazolium salt nucleusand as indicated by the photographic test procedure of Example 1, and asshown in Table 1, it constitutes an excellent electron acceptor andspectral sensitizer, having a speed of 692 and maximum sensitivity at500 m for fogged, photographic reversal emulsions.

In place of the 3-ethyl-2-methyl-6-nitrobenzothiazoliump-toluenesulfonate in the above example, there can be substituted anequivalent amount of other intermediates such as a 3-alkyl (e.g.,methyl, ethyl, propyl, isopropyl, butyl, hexyl, decyl, dodecyl, etc.)-2-methyl 6 nitrobenzoxazolium quanternary salt, e.g., the chloride,bromide, iodide, perchlorate, p-toluenesulfonate, etc. salts, or a3-alkyl (e.g., methyl, ethyl, propyl, isopropyl, butyl, hexyl, decyldodecyl, etc.) -2-methyl-6-nitrobenzoselenazolium quanternary salts,e.g., the chloride, bromide, iodide, perchlorate, p-toluenesulfonate,etc. salts, and the like, to give the corresponding cyanine dyes havinggenerally similar electron acceptor and spectral sensitizer properties,for example, the dye 2-[(3,5-dimethyl 1 phenyl 4 pyrazolyl)vinyl] 3ethyl 6- nitrobenzoxazolium p-toluenesulfonate, the dye 2-[(3,5-dimethyl 1 phenyl 4 pyrazolyl) vinyl] 3 ethyl-6- nitrobenzoselenazoliump-toluenesulfonate, etc. The 3,5- dimethyl l phenyl 4 pyrazolecarboxaldehyde can also be substituted in the above example by anequivalent amount of other related aldehydes such as, for example, 3,5dimethyl 1 phenyl 4 pyrazole acrylaldehyde to give the correspondingcyanine dye 2-[(3,5 dimethyl-1- phenyl 4 pyrazolyl)butadienyl] 3 ethyl 6nitrobenzothiazolium p toluenesulfonate having generally similarproperties as an electron acceptor and spectral sensitizer for fogged,direct positive photographic silver halide emulsions.

A mixture of 1.8 g. (1 mol.) of 1,3,3-trimethyl-2-methylene-1,2-dihydro-3H-pyrrolo[2,3 b]pyridine, 2 g. (1 mol.) of3,5-dimethy1-1-phenyl-4-pyrazole carboxaldehyde, 2.1 g. (mol.) ofp-toluenesulfonic acid, and ml. of acetic anhydride was refluxed for tenminutes. The reaction mixture was chilled and then treated with 100 ml.of ether. The oily layer was separated from the supernatant liquid bydecantation, and washed with ether. The oily layer was disolved inacetone and treated with an aqueous solution of sodium iodide. Afterchilling, the crude dye was collected on a filter and washed with waterand then with acetone. After recrystallization from ethyl alcohol, 1.4g. (29%) of pure dye was obtained as orange plates, M.P. 233235 d.

Analysis.Calcd for C H IN (percent): C, 57.01; H, 5.20; I, 26.21. Found(percent): C, 57.3; H, 5.4; I, 26.4.

The above prepared dye containing the desensitizing3H-pyrrolo[2,3-b]pyridinium salt nucleus was tested by the exactprocedure of Example 1 and found, as shown in Table 1, to have arelative speed of 955, together with other desirable properties setforth in the table, which results indicate that this dye is an excellentelectron acceptor and spectral sensitizer for fogged, photographicreversal emulsions.

EXAMPLE 9 2- (3,5 -dimetl1yl-l-phenyl-4-pyrazolyl vinyl] -1 ,3 ,3trimethyl-5-nitro-3H-indolium p-toluenesulfonate A mixture of 2.4 g. (1mol.) of l,2,3,3-tetramethyl-5- nitro-3H-indolium p-toluenesulfonate,1.25 g. (1 mol.) of 3,5-dimethyl-1-phenyl-4-pyrazole carboxaldehyde, and10 ml. of acetic anhydride was refluxed for ten minutes. The reactionmixture was chilled and the crude dye collected on a filter, washed withacetic anhydride and then with acetone. After recrystallization fromethyl alcohol, 1 g. (28%) of pure dye was obtained as yellow crystals,218-221 D., dec.

Analysis.-Calcd for C LH N O S (percent): C, 64.99; H, 5.64. Found(percent): C, 64.7; H, 5.5.

EXAMPLE 10 5-chloro-2- (3,5-dimethyl-l-phenyl-4-pyrazolyl)vinyl]-3-ethyl-6-nitrobenzothiazolium iodide OzN- O (J2H5 CH 12 EXAMPLE 11 2-(3,5 -dimethyl- 1-phenyl-4-pyrazolyl) vinyl] -3- ethylthiazolo [4,5 -'b]quinolinium chloride C2115 UH;

A mixture of 2.7 g. (1 mol.) of3-ethyl-2-methylthiazolo[4,5-b]quinoliniun1 chloride, 2 g. (1 mol.) of3,5

dimethyl-1-phenyl-4-pyrazole carboxaldehyde, and 10 ml. of aceticanhydride was refluxed two minutes. The reaction mixture was chilled andthe crude dye collected on a filter, washed with acetic anhydride andthen with acetone. After recrystallization from methyl alcohol,

1.8 g. (40%) of pure dye was obtained as orange crystals, M.P. 188-l89C., dec.

The above prepared dyes of Examples 9, 10'and 11 containing thedesensitizing 5-nitro-3H-indolium salt nucleus, the5-chloro-6-nitrobenzothiazolium salt nucleus and thethiazolo[4,5-b]quinolinium salt nucleus, respectively, were tested bythe exact procedure of Example 1 and found, as shown in Table 1, to berelatively good to excellent electron acceptors and spectral sensitizersfor direct positive photographic silver halide emulsions. It

should be noted that the indicated relative speeds are 1000, 603, and1820, respectively, the indicated maximum density in the unexposed areasare 1.62, 1.48 and 1.12 respectively, the indicated minimum density inthe ex posed areas are 0.05, 0.02 and 0.03, respectively, and theindicated maximum sensitization at 545, 500 and 535 m respectively.These results are markedly superior to the comparison dye of Example Awith indicated values of only 1.91 for relative speed, 0.14 for minimumdensity in the unexposed areas, and maximum sensitization at only 455 mFrom the foregoing, it will be apparent that the dye of above Example 9is outstanding in all the desired properties for preparing superiorfogged, photographic reversal emulsions.

EXAMPLE 12 2- 3,5 -dimethy1- 1-phenyl-4-pyrazolyl) vinyl] -1-ethyl-6-nitroquinolinium iodide A mixture of 3.4 g. (1 mol.) of1-ethyl-6-nitro-quinaldiniurn iodide, 2 g. (1 mol.) of3,5-dimethyl-1-pheny1- 4-pyrazole carboxaldehyde, and 15 ml. of aceticanhydride was refluxed ten minutes. The reaction mixture was chilled andtreated with ml. of ether. The oily layer was separated from thesupernatant liquid by decantation and then treated with ethyl alcohol.The crude dye was extracted with 450 ml. of methyl alcohol. The filtratewas concentrated to 25 ml. and chilled, and the dye collected on afilter. After recrystallization from methyl alcohol, 0.2 g. (4%) of puredye was obtained as brownish crystals, M.P. 128131 D., dec.

Photographic testing in accordance with the procedure of Example 1indicated that the above prepared dye containing the desensitizing6-nitroquinolinium salt nucleus, is a moderately good electron acceptorand spectral sensitizer for fogged, photographic reversal emulsions. Theresults are listed in Table 1 hereinafter.

13 EXAMPLE 13 1,3 -diallyl-2-[ 1-phenyl-4-pyrazolyl) vinyl] imidazo [4,5-b] quinoxalinium p-toluenesulfonate A mixture of 4.4 g. (1 mol.) of1,3-diallyl-2-methylimidazo[4,5-b]quinoxalinium p-toluenesulfonate, 1.7g. (1 mol.) of 1-phenyl-4-pyrazole carboxaldehyde, and ml. of aceticanhydride was refluxed ten minutes. The reaction mixture was chilled andthe crude dye collected on a filter and washed with acetone. Afterrecrystallization from methyl alcohol, 3.2 g. (54%) of pure dye wasobtained as brownish crystals, M.P. 232-233 C., dec.

EXAMPLE 14 6-chloro- 1, 3 -diphenyl-2- 1 -phenyl-4-pyrazolyl vinyl]imidazo[4,5-b] quinoxalinium p-toluenesulfonate A mixture of 5.4 g. (1mol.) of 6-chloro-1,3-diphenyl- Z-methylimidazo [4,5 -b] quinoxaliniump-toluenesulfonate, 1.7 g. (1 mol.) of 1-phenyl-4-pyrazolecarboxaldehyde, and 10 ml. of acetic anhydride was refluxed ten minutes.The reaction mixture was chilled and the crude dye collected on a filterand washed with acetone. After recrystallization from methyl alcohol,3.4 g. (49%) of pure dye was obtained as yellowish plates, M.P. 291292C., dec.

The dyes of above Examples 13 and 14, each containing a desensitizing1,3-diallylimidazo [4,5-b1quinoxalinium salt nucleus, were tested by theexact procedure of Example 1 and found, as shown in Table 1 hereinafter,to be relatively good electron acceptors and spectral sensitizers forfogged, direct positive photographic silver halide emulsions. The dye ofExample 13 showed the best relative speed of 603 as compared to 263 forthe dye of Example 14. In all other properties both dyes were about thesame.

EXAMPLE 15 3-ethyl-6-nitro-2-[ 1-phenyl-4-pyrazolyl)vinyl]benzothiazoliu-m p-toluenesulfonate H s 6 ON I OCH=OHC/ 3 3/ \O/ $.11.Ill o soqrr,

A mixture of 4 g. (1 mol.) of 1-ethyl-2-methyl-6-nitrobenzothiazoliump-toluenesulfonate, 1.7 g. (1 mol.) of 1-phenyl-4-pyrazolecarboxaldehyde, and 15 ml. of acetic anhydride was refluxed ten minutes.The reaction mixture was chilled and the crude dye collected on a filterand washed with acetone. After recrystallization from methyl alcohol,3.9 g. (71%) of pure dye was obtained as orange crystals, M.P. 276277C., dec.

14 EXAMPLE 16 3-ethyl-6-nitro-2- 1,3,5 -trimethyl-4-pyrazolyl) vinyl]benzothiazolium p-toluenesulfonate A mixture of 4 g. (1 mol.) of3-ethyl-2-methyl-6- nitrobenzothiazolium p-toluenesulfonate, 1.4 g. (1mol.) of 1,3,S-trimethyl-4-pyrazole carboxaldehyde, and 15 ml. of aceticanhydride was refluxed ten minutes. The reaction mixture was chilled andthe crude dye collected on a filter and washed with acetone. Afterrecrystallization from methyl alcohol, 3.5 g. (69%) of pure dye wasobtained as brown needles, M.P. 253-254" C., dec.

The above prepared dyes of Examples 15 and 16 containing thedesensitizing 6-nitrobenzothiazolium salt nucleus were tested by theprocedure described in Example l and found, as shown in Table 1hereinafter, to be moderately good electron acceptors and spectralsensitizers (with relative speeds of 398 and 479, respectively) forfogged, direct positive photographic silver halide emulsions.

The dyes prepared according to the above Examples 1 to 16, together withthe comparison dye of Example A, as indicated previously, werephotographically tested by the exact procedure described in Example 1herein. The results are shown in Table 1 immediately below.

TABLE 1 Relative density Dye conc., White Maximum Minimum SensigJmolelight clear in unex in exposed tizing silver speed posed areas areasmax. (m

0. 500 603 1. 76 0. 03 485 0. 685 295 1. 74 0. 06 485 0.810 575 1. 96 0.04 510 0. 790 398 l. 71 0. 05 490 0. 970 380 1. 78 0. O4 500 0. 860436 1. 84 0. 04 500 0. 700 692 1. 56 0. 02 500 0. 700 955 1. 76 0. 02508 0. 700 1, 000 1. 62 0. 05 545 0. 700 603 1. 48 0. 02 500 0. 700 1,820 1. 12 0. 03 535 0. 700 240 1. 11 0. 08 450 0. 700 603 1. 54 0. 03600 0. 700 263 1. 58 0. 10 500 0. 700 398 1. 52 0. 03 485 16 0. 700479 1. 40 0. 03 490 Example A- 0. 350 191 1. 50 O. 14 455 The followingexamples further illustrate the preparation of fogged, direct positivephotographic emulsions and elements with the cyanine dyes of theinvention.

EXAMPLE 17 To 9.0 pounds of a silver chloride gelatin emulsioncontaining an equivalent of grams of silver nitrate is added 0.017 gramof 1,3-diallyl-2-[(3,5-dimethyl-1- phenyl 4 pyrazolyl)vinyl]imidazo[4,5-b] quinoxalinium iodide (dye of Example 1). The emulsion is coatedon a non-glossy paper support, and is flashed with white light to give adensity of 1.2 when developed in the following developer, diluted 1 partto 2 parts of water:

N-methyl-p-aminophenol sulfate-3.1 grams Sodium sulfite, des.-45 gramsHydroquinone12 grams Sodium carbonate, des.67.5 grams Potassiumbromide1.9 grams Water to-1 liter The light fogged material can beexposed to an image with light modulated by a Wratten No. 15 filter togive a direct positive image. Similar results are obtained when the dyeof Example 3 is substituted for the 1,3-diallyl-2- 1 (3,5dimethyl-1-phenyl-4-pyrazolyl) vinyl]imidazo [4,5- b] quinoxaliniumiodide.

EXAMPLE 18 Seven pounds of a silver chloride gelatin emulsion containingthe equivalent of 100 g. of silver nitrate is heated to 40 C. and the pHis adjusted to 7.8. Eight cc. of full strength (40%) Formalin solutionis added and the emulsion is held at 40 C. for minutes. At the end ofthe holding period, the pH is adjusted to 6.0 and 0.125 g. of 2-[(3,5dimethyl-1-phenyl-4-pyrazolyl)vinyl]-3-ethyl-6-nitrobenzothiazolium-p-toluenesulfonate (dye of Example 7) is added tothe emulsion. The emulsion is coated on a support, and provides gooddirect positive images. Similar results are obtained when the dye ofExample 9 is substituted for the 2-[3,5-dimethyl-1-phenyl-4-pyrazolyl)vinyl]-3-ethyl-6-nitrobenzothiazolium-ptoluenesulfonate.

By substituting other dye compounds of the invention, into the procedureof the above Examples 17 and 18, and more particularly the dyes ofExamples 2, 4-6, 8 and 10-16, generally similar fogged, direct positivephotographic silver halide emulsions and photographic elements may beprepared.

The photographic silver halide emulsion and other layers present in thephotographic elements made according to the invention can be hardenedwith any suitable hardener, including aldehyde hardeners such asformaldehyde, and mucochloric acid, aziridine hardeners, hardeners whichare derivatives of dioxane, oxypolysaccharides such as oxy starch or oxyplant gums, and the like. The emulsion layers can also containadditional additives, particularly those known to be beneficial inphotographic emulsions, including, for example, lubricating materials,stabilizers, speed increasing materials, absorbing dyes, plasticizers,and the like. These photographic emulsions can also contain in somecases additional spectral sensitizing dyes. Furthermore, these emulsionscan contain color forming couplers or can be developed in solutionscontaining couplers or other color generating materials. Among theuseful color formers are the monomeric and polymeric color formers, e.g.pyrazolone color formers, as Well as phenolic, heterocyclic and openchain couplers having a reactive methylene group. The color formingcouplers can be incorporated into the direct positive photographicsilver halide emulsion using any suitable technique, e.g., techniques ofthe type shown in Jelley et al. US. Pat. 2,322,027, issued June 15,1943, Fierke et al. US. Pat. 2,801,171, issued July 30, 1957, FisherU.S. Pats. 1,055,155 and 1,102,028, issued Mar. 4, 1913, and June 30,1914, respectively, and Wilmanns US. Pat. 2,186,849, issued Jan. 9,1940. They can also be developed using incorporated developers such aspolyhydroxybenzenes, aminophenols, 3-pyrazolidones, and the like.

Light sensitive photographic silver halide emulsions containing thenovel dyes of this invention are claimed in my US. patent applicationSer. No. 604,146, titled Photographic Emulsions, filed concurrently withthe instant application.

Although the invention has been described in considerable detail withparticular reference to certain preferred embodiments thereof, it willbe understood that variations and modifications can be effected withinthe spirit and scope of the invention as described hereinabove, and asdefined in the appended claims.

I claim:

1. A cyanine dye selected from those represented by the followinggeneral formula:

wherein m represents a positive integer of from 1 to 2; n represents apositive integer of from 2 to 3; L represents a methine linkage; Rrepresents a member selected from the group consisting of an alkyl groupof from 1 t0 4 carbon atoms, an alkenyl group, and a phenyl group", Rand R each represents a member selected from the group consisting of ahydrogen atom, an alkyl group of from 1 to 4 carbon atoms and a phenylgroup; R represents a member selected from the group consisting of analkyl group of from 1 to 4 carbon atoms and a phenyl group; X representsan acid anion; and, Z represents the non-metallic atoms necessary tocomplete a desensitizing heterocyclic nucleus containing 5 to 6 atoms inthe heterocyclic ring, said desensitizing nucleus being selected fromthe group consisting of nitrobenzothiazole, nitrobenzoselenazole,imidazo [4,5-b] quinoxaline, 3,3-dialkyl- I 3H-pyrrolo[2,3-b]pyridine,3,3-dialkyl 3H nitroindole, thiazolo[4,5 b]quinoline, nitroquinoline,nitrothiazole,

nitronaphthothiazole, nitrooxazole, nitronaphthoxazole,

nitroselenazole, nitronaphthoselenazole and nitropyridine nuclei, thealkyl groups in said desensitizing nuclei containing from 1 to 4 carbonatoms.

2. A cyanine dye as defined in claim 1 wherein said n represents theinteger 2.

3. A cyanine dye as defined by claim 1 .wherein said Z represents thenon-metallic atoms necessary to complete a nitrobenzothiazole nucleus.

4. A cyanine dye as defined by claim 1 wherein said Z represents thenon-metallic atoms necessary to complete a nitrobenzoxazole nucleus.

5. A cyanine dye as defined by claim 1 ,wherein said Z represents thenon-metallic atoms necessary to complete a nitrobenzoselenazole nucleus.

6. A cyanine dye as defined by claim 1 ,wherein said Z represents thenon-metallic atoms necessary to complete an imidazo [4,5-b] quinoxalinenucleus.

7. A cyanine dye as defined by claim 1 wherein said Z represents thenon-metallic atoms necessary to complete a3,3-dialkyl-3H-pyrrolo[2,3-b]pyridine nucleus.

8. A cyanine dye as defined by claim 1 wherein said Z represents thenon-metallic atoms necessary to complete a 3,3-dialkyl-3H-nitroindolenucleus.

9. A cyanine dye as defined by claim 1 wherein said Z represents thenon-metallic atoms necessary to complete a thiazolo [4,5b]quinolinenucleus.

10. A cyanine dye as defined by claim 1 wherein said Z represents thenon-metallic atoms necessary to com-' plete a nitroquinoline nucleus.

11. A cyanine dye selected from the group consisting of 1,3 -diallyl-2-[(3,5-dimethyl-1-phenyl-4-pyrazolyl) vinyl] imidazol [4,5 -b]quinoxalinium salt,

2-[ (3,5 -dimethyl- 1-phenyl-4-pyrazolyl vinyl] -l,3-diethylimidazo [4,5-b] quinoxalinium salt,

6-chloro-2- (3,5 -dimethyl- 1-phenyl-4-p yrazolyl) vinyl]1,3-diphenylimidazo [4,5 -b] quinoxalinium salt,

2-[ (3,5 -dimethyl-l-phenyl-4-pyrazolyl vinyl] -1,3-diphenylimidazo [4,5-b] quinoxalinium salt,

1,3-diallyl-6-chloro-2-[ (3,5 -dimethyl- 1-phenyl-4-pyrazolyl)vinyl]imidazo [4,5 -b quinoxalinium salt,

1,3-diallyl-6-chloro-2- (1,3,5-trimethyl-4-pyrazolyl) vinyl] imidazo[4,5 -b] quinoxalinium salt,

2-[ (3 ,5 -dimethyl- 1 -phenyl-4-pyrazolyl) vinyl] -3-ethyl-6-nitrobenzothiazolium salt,

2- (3,5 -dimethyl- 1-phenyl-4-pyrazolyl) vinyl]1,3,3-trimethyl-3H-pyrrolo [2,3-b] pyridinium salt,

2- 3,5 -dimethyl- 1 -phenyl-4-pyrazoly1) vinyl] l ,3,3-trimethyl-5-nitro-3 H-indolium salt,

5 -chloro-2- (3,5 -dimethyl- 1-phenyl-4-pyrazolyl) vinyl]3-ethyl6-nitrobenzothiazolium salt,

2-[ (3,5-dimethyl- 1-pheny1-4-pyrazolyl) vinyl] -3-ethylthiazolo [4,5-b] quinolinium salt,

2-[ 3,5 -dimethyll-phenyl-4-pyrazolyl) vinyl] 1-ethyl-6-nitroquinolinium salt,

1,3-dial1yl-2-[( 1-pheny1-4-pyrazolyl) vinyl] imidazo [4,5

b] quinoxalinium salt,

6-chl0ro-1,3-diphenyl-2-[ 1-pheny1-4-pyrazolyl) vinyl] imidazo [4,5-bquinoxalinium salt,

3-ethyl-6-nitro-2-[ 1-phenyl-4-pyrazolyl) vinyl] benzothiazolium salt,and

3-e'thyl-6-nitro -2- ['(;1,3 ,S-trimethyl-4-pyrazo1yl vinyl]benzothiazolium salt.

18 FOREIGN PATENTS 797,144 6/1958 England.

JOHN D. RANDOLPH, Primary Examiner US. Cl. X.R.

